A liquid crystal display mainly includes components such as a backlight module, a display panel, and an outer frame. According to the direction of a light source, a backlight module can be further divided into an edge type backlight module and a direct type backlight module. Currently, a medium-sized and large-sized liquid crystal display using a light-emitting diode (LED) as a backlight module light source has a direct type backlight module with local dimming function in order to display high dynamic range (HDR) and high contrast requirements. A characteristic of the light-emitting diode is that it has strong positive light. Therefore, a structure design of the direct type backlight module is to convert a light of the light-emitting diode into a uniform surface light source and then illuminate a display panel.
A backlight module of a liquid crystal display has a backlight chamber. A plurality of light emitting diodes may be located at the bottom of the backlight chamber, and a diffusion plate may be disposed above the backlight chamber. When a thickness of the backlight chamber is sufficient, a light of the light-emitting diodes can be sufficiently diffused in the backlight chamber to obtain a uniform surface light source. However, if the thickness of the backlight chamber is reduced in order to reduce overall backlight module thickness, more light-emitting diodes must be disposed at the bottom of the backlight chamber to reduce spacing between the light-emitting diodes and to improve the uniformity of the surface light source, but it also caused an increase in cost.
In addition to deposing more light-emitting diodes in a backlight chamber, another way to reduce a thickness of a backlight chamber and maintain or even increase the uniform light diffusion effect is to diffuse a light from the light-emitting diode in the backlight chamber first. However, since the light-emitting diode has a strong positive light, even if a divergence angle of the light of the light-emitting diode is diffused by optical lens, a bright spot is still found above the light-emitting diode during an actual measurement. In addition, the light of the light-emitting diode has a limited diffusion distance in the backlight chamber, thus limiting a thickness of the backlight chamber that can be reduced.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.